qt - QStyledItemDelegate: how to make checkbox button to change its state on click -

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i have delegate mydelegate used qlistwidget. delegate derived qstyleditemdelegate. 1 of goals of mydelegate place checkbox button on each row of listwidget. done within paint() event of mydelegate: 

void mydelegate::paint(qpainter *painter, const qstyleoptionviewitem &option, const qmodelindex &index) const {     qstyleditemdelegate::paint(painter, option, index);     // ... drawing other delegate elements      qstyleoptionbutton checkbox;     // setting checkbox's size , position      // draw checkbox     qapplication::style()->drawcontrol(qstyle::ce_checkbox, &checkbox, painter); }

at first thought checkbox automatically change state on click, since specified qstyle::ce_checkbox. not case. looks have specify checkbox visual behavior manually.

data-wise, when user clicks on checkbox, signal emitted , scene data changed. perform action in editorevent():

bool mydelegate::editorevent(qevent *event, qabstractitemmodel *model, const qstyleoptionviewitem &option, const qmodelindex &index)   {     if (event->type() == qevent::mousebuttonrelease) {         if (/* within checkbox area */)             emit this->clickedcheckbox(index);     } }

the backend part works. however, cannot figure out how make checkbox button change visual state checked unchecked, , backwards.

i realized can change checkbox state manually doing paint():

checkbox.state = somecondition? (qstyle::state_enabled | qstyle::state_on) :                            (qstyle::state_enabled | qstyle::state_off) ;

qstyle::state_on/off trick of manual checkbox state change.

but not know how set somecondition , should set up. tried introduce private bool variable set in editorevent() when checkbox area gets click, however, not produce desired behavior: sets other checkboxes of listwidget same visual state. so, behaved global condition checkboxes.

i feel like, accomplish task, have re-implement button , make change checkbox state on click. i'm lost on way , not sure how approach problem. qstyleoptionbutton api not see clicked() or other method use.

so, question is: how make checkbox behave checkbox, visually? if need re-implement checkbox, class inherit?

you can set value describes checkbox state in mydelegate::editorevent , use paint proper checkbox:

const int check_role = qt::userrole + 1;  bool mydelegate::editorevent(qevent *event,                             qabstractitemmodel *model,                             const qstyleoptionviewitem &option,                             const qmodelindex &index) {     if (event->type() == qevent::mousebuttonrelease)     {         bool value = index.data(check_role).tobool();          // invert checkbox state         model->setdata(index, !value, check_role);          return true;     }      return qstyleditemdelegate::editorevent(event, model, option, index); }  void mydelegate::paint(qpainter *painter,                        const qstyleoptionviewitem &option,                        const qmodelindex &index) const {     qstyleoptionbutton cbopt;     cbopt.rect = option.rect;      bool ischecked = index.data(check_role).tobool();     if (ischecked)     {         cbopt.state |= qstyle::state_on;     }     else     {         cbopt.state |= qstyle::state_off;     }      qapplication::style()->drawcontrol(qstyle::ce_checkbox, &cbopt, painter); }

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